Refined Model for Interpreting Shallow Penetration CPTs in Sands

Puech, Alain J.; Foray, Pierre

doi:10.4043/14275-ms

Cited by 23 publications

(16 citation statements)

References 4 publications

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“…In other words, for large particles the penetrometer can advance by rearranging a few neighbouring particles rather than setting into motion a whole mass of material around the tip that can form a shearing plane, as with smaller particles, e.g. Puech & Foray (2002). Figure 25 shows the pressure-depth gradient plotted against the particletip diameter ratio for impacts of ACC-E into the same granular targets as used for X-PEN in figure 24.…”

Section: Characterisation Of Granular Materialsmentioning

confidence: 99%

Detection of structure in asteroid analogue materials and Titan’s regolith by a landing spacecraft

Paton

Green

Ball

et al. 2016

Advances in Space Research

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We compare measurements made by two impact penetrometers of different sizes and with different tip shapes to further understand penetrometer design for performing pentrometry on an asteroid. To this end we re-visit the interpretation of data from the Huygens' penetrometer, ACC-E, that impacted Titan's surface. In addition we investigate the potential of a spacecraft fitted with a penetrometer to bounce using a test rig, built at The Open University (UK).Analysis of ACC-E laboratory data, obtained from impacts into ∼4 mm diameter gravel, was found to produce an unusual decrease in resistance with depth (force-depth gradient) which was also seen in the Huygens' ACC-E data from Titan and originally interpreted as a wet or moist sand. The downward trend could also be reproduced in a hybrid Discrete Element Model (DEM) if it was assumed that the near surface particles are more readily * Corresponding author mobilised than those deeper in the target. With regard to penetrometer design penetration resistance was found to be sensitive to the ratio of particle to tip diameter. A clear trend was observed with a conical tip penetrometer, X-PEN, of decreasing force-depth gradients with increasing particle sizes most likely due to a transformation from a bulk displacement of material by the penetrating tip to more local interactions. ACC-E, which has a hemispherical tip, was found to produce a wider range of force-depth gradients than X-PEN, which had a conical tip, possibly due to difficulties dislodging jammed particles. Both penetrometers were able to determine particle diameter and mass after post-processing of the data.Laboratory simulations of landings with the test rig suggest that a large impact penetrometer under certain circumstances could absorb a significant amount of the elastic energy of the spacecraft possibly aiding landing. Alternatively a small impact penetrometer would allow the spacecraft to bounce freely off the surface to make a measurement at another location.

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Section: Characterisation Of Granular Materialsmentioning

confidence: 99%

Detection of structure in asteroid analogue materials and Titan’s regolith by a landing spacecraft

Paton

Green

Ball

et al. 2016

Advances in Space Research

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show abstract

“…This then allowed a repeatable preparation of the target which was required for investigating speed related effects. The target was assumed to fail along the slip lines as shown in figure 9 by dilation (Puech & Foray, 2002) and therefore no significant compaction of the material over time was expected.…”

Section: Propertymentioning

confidence: 99%

“…The friction factor, K, governs the forces between the disturbed zone and the target at rest. A value of K = 0.7 was found empirically by Puech & Foray (2002) through a curve fitting procedure to multiple CPT soundings in sand. The the lateral extension of the slip lines, L, can be expressed as follows.…”

Section: Forces On the Penetrometer Tipmentioning

confidence: 99%

“…The friction angle is very sensitive to the compaction and can be related to the relative density (Puech & Foray, 2002). We will examine the friction angle here to characterise the materials impacted by the experimental cone penetrometer (X-PEN).…”

Section: Tests In Loose and Compacted Regolith Analoguesmentioning

confidence: 99%

“…The very loose layer on top was most likely created during the repairing of the crater from two drop tests made during a rehearsal for the experiment. After two rehearsal drop tests the target was prepared by stirring this top layer which probably remained loose possibly because the shearing mechanism in the surface layers is due to dilation (Puech & Foray, 2002). The denser layer may be a remnant from previous drops too.…”

Section: Speed Testsmentioning

confidence: 99%

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Using the inertia of spacecraft during landing to penetrate regoliths of the Solar System

Paton

Green

Ball

et al. 2015

Advances in Space Research

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The high inertia, i.e. high mass and low speed, of a landing spacecraft has the potential to drive a penetrometer into the subsurface without the need for a dedicated deployment mechanism, e.g., during Huygens landing on Titan. Such a method could complement focused subsurface exploration missions, particularly in the low gravity environments of comets and asteroids, as it is conducive to conducting surveys and to the deployment of sensor networks. We make full-scale laboratory simulations of a landing spacecraft with a penetrometer attached to its base plate. The tip design is based on that used in terrestrial Cone Penetration Testing (CPT) with a large enough shaft diameter to house instruments for analysing pristine subsurface material. Penetrometer measurements are made in a variety of regolith analogue materials and target compaction states. For comparison a copy of the ACC-E penetrometer used on the Huygens mission is used. A test rig at the Open * Corresponding author University is used and is operated over a range of speeds from 0.9 to 3 m sand under two gravitational accelerations. The penetrometer was found to be sensitive to the target's compaction state with a high degree of repeatability. The penetrometer measurements also produced unique pressure profile shapes for each material. Measurements in limestone powder produced an exponential increase in pressure with depth possibly due to increasing compaction with depth. Measurements in sand produced an almost linear increase in pressure with depth. Iron powder produced significantly higher pressures than sand presumably due to the rough surface of the grains increasing the grain-grain friction. Impacts into foamglas produced with both ACC-E and the large penetrometer produced an initial increase in pressure followed by a leveling off as expected in a consolidated material. Measurements in sand suggest that the pressure on the tip is not significantly dependent on speed over the range tested, which suggests bearing strength equations could be applied to impact penetrometry in sand-like regoliths.In terms of performance we find the inertia of a landing spacecraft, with a mass of 100 kg, is adequate to penetrate regoliths expected on the surface of Solar System bodies. Limestone powder, an analogue for a dusty surface, offered very little resistance allowing full penetration of the target container. Both iron powder, representing a stronger coarse grained regolith, and foamglas, representing a consolidated comet crust, could be penetrated to similar depths of around two to three tip diameters, probably more if impacting with a slightly higher speed.

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Applicability of soil‐type index for shear wave velocity‐based liquefaction assessment

Ecemis,

Monkul,

Orucu

2024

Earthq Engng Struct Dyn

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The current simplified liquefaction assessment method based on the shear‐wave velocity, Vs has uncertainties about how the fine contents change the Vs‐based liquefaction resistance. According to the simplified method, for a given Vs, the cyclic resistance ratio (CRR) increases with an increase in fine contents. However, field investigations recently revealed that for various silty sands, the correlation between CRR and Vs is soil‐type index dependent and not specific for all sand‐silt mixtures with the same fine contents. Therefore, a detailed experimental research program is performed in this study to clarify the effect of the soil‐type index on the shear wave velocity and CRR correlation. In the first part of the present study, the cyclic resistance of sand mixed with non‐plastic (NP) fines (dry weight of 0%, 5%, 15%, and 35%) was investigated using cyclic direct simple shear (CDSS) tests. Seismic cone penetration (SCPT) tests were performed inside the large‐scale box to facilitate normalized cone penetration resistance (qc1N) and shear wave velocity measurements on the soils used in the CDSS tests. A new correlation was proposed between the qc1N and normalized shear wave velocity (Vs1) using the soil‐type index Ic representing the behavior of soil. Then, CRR‐Vs1 correlation was obtained experimentally for four distinct ranges of soil‐type index. Finally, the results of this study and the proposed CRR‐Vs1 trends in other investigations were used to discuss the soil‐type dependent Vs‐based liquefaction susceptibility zones.

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Refined Model for Interpreting Shallow Penetration CPTs in Sands

Cited by 23 publications

References 4 publications

Detection of structure in asteroid analogue materials and Titan’s regolith by a landing spacecraft

Detection of structure in asteroid analogue materials and Titan’s regolith by a landing spacecraft

Using the inertia of spacecraft during landing to penetrate regoliths of the Solar System

Applicability of soil‐type index for shear wave velocity‐based liquefaction assessment

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